Date of Award
Master of Science
Gail R. Nonnecke
C. L. Burras
Sustainable grape production entails the implementation of management practices that control weeds, maintain grapevine performance, and conserve soil quality. Conventional weed management practices include herbicide application and/or cultivation. These practices compromise soil quality by limiting additions of organic matter and exposing the soil surface, thereby leaving it prone to degradative processes. With the expansion of continental climate viticulture in areas with rain-fed agriculture, such as in the Midwest, there is a need for sustainable weed management practices that optimize production while conserving soil quality. The primary objective of this investigation was to evaluate weed management practices in an established midwestern vineyard. Sub-objectives of the investigation addressed within individual experiments include: 1) comparing conventional and alternative weed management practices on weed control, grapevine performance, and soil quality, and 2) evaluating the influence of irrigation on grapevine growth and development, grown with and without a living mulch, on mitigation of water competition. An additional objective of this investigation was to survey Iowa fruit growers' attitudes and awareness of weed management practices that conserve soil resources.
In the first experiment, two conventional and two alternative weed management strategies were compared in an established Iowan vineyard with `Marychal Foch' grapevines (Vitis rupestris Scheele yvinifera L.). Treatments were replicated four times in a randomized complete block design and included: 1) cultivation, 2) herbicide application, 3) straw mulch, and 4) a living mulch of creeping red fescue (Festuca rubra L. `Pennlawn'). Straw and living mulches controlled weed populations and grapevine yield did not differ among the treatments. Dormant cane pruning weights and fruit quality were lowest in cultivated and straw mulch plots, respectively. Mulched plots had greater water-filled pore space and water content, as well as faster infiltration rates. No differences in chemical soil quality attributes were observed. Although earthworm populations were greater in straw mulch plots, no differences in soil enzymatic activity were found. Results from the experiment demonstrate straw and living mulches reduce weed populations, maintain grapevine productivity, and improve several indicators of soil quality.
The effects of living mulches, with and without irrigation, on grapevine growth and development were measured in the second experiment. Data were collected from an established vineyard in Iowa with `Reliance' and `Swenson Red' grapevines (Vitus labrusca L.) planted in a randomized complete block design. Treatments were replicated eight times and included: 1) herbicide application without irrigation, 2) herbicide application with irrigation, 3) living mulch without irrigation, and 4) living mulch with irrigation. The living mulch treatment was a mixture of shade-tolerant creeping red and Chewings fescue [Festuca rubra L. `Foxy' and F. rubra var. fallax (Thuill.) Hack. `Ambrose,' respectively]. Supplemental irrigation was provided via drip irrigation and scheduling regimes were based on fescue evapotranspiration. Living mulches and irrigation had no consistent effect on grapevine growth and development, suggesting little-to-no competition existed between the grapevines and living mulches during the period in which the study was conducted. When compared to both herbicide-treated plots, living mulches reduced weed populations and promoted several indicators of soil quality.
Results from both experiments demonstrate the alternative practices of straw and living mulches control weeds, maintain grapevine performance, and may be viable alternatives to vineyard weed management that promotes soil quality within the Midwest. While results from the experiments suggest alternative weed management practices may contribute to the sustainability of a weed management system, grower receptiveness to alternative practices is important when planning future extension-education programs and advancing soil-quality awareness. Within a survey of twenty-two Iowa fruit growers, all survey participants were aware of soil quality and considered the quality of their soils when making land management decisions. Most were aware of alternative weed management practices, yet were uncertain about the outcome of implementing alternative practices within their own production systems. To further advance the awareness and adoption of soil-quality concepts and alternative weed management practices, respectively, future extension programs should focus on educating growers how weed management decisions can impact both crop productivity and soil quality.
Lisa Marie Wasko
Wasko, Lisa Marie, "Alternative weed management practices: Effects on weed control, grapevine performance, and soil quality in an established midwestern vineyard" (2010). Graduate Theses and Dissertations. 11405.